Primate Monocytes - CD14, CD16 - Ziegler-Heitbrock

MUTZ-3, a monocytic model cell line for interleukin-4 and lipopolysaccharide studies

Abstract

The human monocytic cell lines MUTZ 3 and MONO MAC B express the lipopolysaccharide (LPS) receptor CD14. Paralleling the situation in peripheral blood monocytes (PBMo), recombinant human interleukin 4 (IL 4) down regulated the expression of CD14 on the cell surface of MUTZ 3, but not that of MONO MAC 6 cells. In addition, preincubation with IL 4 prevented the LPS induced up regulation of IL 1 beta mRNA levels in MUTZ 3, but not in MONO MAC 6 cells. We examined whether the differential responsiveness of the cell lines was due to the missing expression of the IL 4 receptor (IL 4R) alpha or gamma(c) chain in MONO MAC 6 cells. Flow cytometric and immunoprecipitation analysis revealed expression of both IL 4R chains in both cell lines. In addition, short term stimulation with IL 4 induced tyrosine phosphorylation of the gamma(c) chain. As both cell lines also expressed signal transducer and activator of transcription 6 (STAT 6), our data suggested that the differential reaction patterns of MUTZ 3 and MONO MAC 6 cells were not due to a generally defective IL 4R complex. Interestingly, long term (48 hr) treatment with LPS rendered MONO MAC 6 cells sensitive to IL 4. LPS up regulated expression of monocyte specific esterase (MSE) mRNA as well as CD14 protein in MONO MAC 6 cells; both effects were inhibited by IL 4. This stimulation was not paralleled by an increase of IL 4R mRNA or protein expression supporting the above hypothesis of a constitutively present and active IL 4R. We discuss possible causes for the differential reaction patterns of MUTZ 3 and MONO MAC 6 cells to IL 4.